Dormancy and longevity of annual ryegrass (Lolium rigidum) as affected by soil type, depth, rainfall, and duration of burial

Abstract

Effects of soil type, time, depth of seed burial and rainfall pattern were investigated on the longevity of glyphosate resistant annual ryegrass (Lolium rigidum Gaudin) in the northern summer rainfall dominant grain region of Australia in a 16 month experiment conducted under polyhouse conditions. Lolium rigidum seeds placed in nylon bags were buried in pots at 5 and 10 cm depth in either Laureldale (clay) or Kirby (sandy loam) soil receiving simulated rainfall representing a Tamworth (summer) and Hamilton (winter) rainfall environment of Australia. The bags were exhumed every four months and tested for percent viable, germinable, dormant and dead seeds. In the short term (several months), factors such as soil type, rainfall and depth of burial affected the fate and condition of L. rigidum seeds and emergence pattern of seedlings. However, irrespective of treatment, all seeds lost their viability after 16 months of burial. Hence, in the longer term, L. rigidum behaviour in this summer dominant rainfall environment with different soils is likely to be similar to that where the weed occurs more commonly in the southern Mediterranean regions of Australia. Maximum emergence in the polyhouse occurred during mid autumn similar to that in the field. The results from this experiment will allow for the development of management strategies which may enhance the depletion of the soil seedbank of viable L. rigidum seeds in the shortest possible time.

Variability in Mediterranean annual grassland diversity driven by small-scale changes in fertility and radiation

“…This finding coincides with the positive relationship identified with soil P in our results. It has also been reported in previous studies that Echium plantagineum responds positively to soil clay content (Narwal et al 2008), which seems to be consistent with the strong negative relationship identified between the distribution of the species and soil bulk density. According to other studies (González Ponce and Sentín Montoya 2007), the populations of Lolium rigidum are positively influenced by N fertilizers (González Ponce and Sentín Montoya 2007) which can be explained by the low N mineralization rate of the plots where it is most abundant.…”

Soil type does not affect seed ageing when soil water potential and temperature are controlled

“…2). Several earlier studies have investigated the role of soil type in determining seed persistence but their results are not conclusive (Bekker et al 1998;Narwal et al 2008;Van et al 2005;Wu et al 2007). Each of these studies identified differences in seed persistence between soils, but it is difficult to distinguish the degree of influence imparted by soil types as distinct from temperature and hydrological conditions, which may also have varied between sites or potted soils, but were not reported.…”

“…Some studies have specifically targeted the influence of soil type and nutrient status on seed persistence (e.g. (Bekker et al 1998;Benvenuti 2003;Narwal et al 2008;Wu et al 2007). However, with the exception of Wu et al (2007), experiments were conducted under controlled glasshouse conditions, or in soils at different locations, and therefore under unnatural or disparate climates, and the soil water and temperature conditions were not described.…”

Which soils are comfortable for oilseed rape seeds (Brassica napus) to survive?

“…All following rainfall was the same for both areas and soils, thus the results could only refer to the differences in soil. Annual ryegrass (Lolium rigidum) seeds from a pot experiment had a greater number of viable and primarily dormant seeds surviving in a sandy loam compared to a clay soil (Narwal et al 2008), but this grass species had a generally short survival time, and there was no further induction of dormancy. In contrast, OSR seeds survive 10 years and more (Lutman et al 2003, D'Hertefeldt et al 2008, and primary dormancy is usually zero or low in mature seeds (Gruber et al 2004).…”

“…Thus all surviving OSR seeds in the current study must have fallen dormant during seed burial. Consequently, if clay soils tend to provide conditions for non-dormant seeds to perish (Narwal et al 2008), seeds with long-term dormancy or dormancy induction such as OSR could well survive.…”